Detecting nuclear debris from a nuclear weapon exploded in or substantially vented to the Earth's atmosphere constitutes the most certain indication that a violation of the Comprehensive Test Ban Treaty has occurred. For this reason, a radionuclide portion of the International Monitoring System is being designed and implemented. The IMS will monitor aerosols and gaseous xenon isotopes to detect atmospheric and underground tests, respectively. The monitoring network will be composed of a number of manual or automatic stations which have the capacity to sample large volumes of air each day and make sensitive gamma-ray spectroscopy measurements of the samples collected. In addition, a number of Certified Laboratories will perform confirmatory measurements on samples that show detectable quantities of fission products. This may be accomplished by measuring (instrumentally or by radiochemical means) certain isotopes which discriminate weapons debris from reactor accidents and other releases of fission products. An automated system, the Radionuclide Aerosol Sampler/Analyzer (RASA), has been developed at Pacific Northwest National Laboratory to meet CTBT aerosol measurement requirements. This is achieved by the use of a novel sampling apparatus, a high-resolution germanium detector, and very sophisticated software.
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